It’s not based directly on Device age, it is based on security and features as “makes more sense” as was mentioned. 
In theory, you can continue to use any device of any age, even something from a decade ago…IF your device manufacturer continued to support giving it updates all the way up to or past Android 7 and iOS 12.
I’ll elaborate on this a little for those who are interested and detail-oriented like me. I’m mostly just describing WHY there is an issue, not necessarily ideals of what SHOULD BE, etc.
The problem is that device manufacturers (not app creators) want you to buy a new device because it’s the only way they bring in more money, so they will refuse to provide support for those devices because they would have to pay someone to provide that support, but they would get little to nothing in return out of it, causing them to basically just lose money. In contrast, if they stop supporting it within a couple of years and don’t LET you get the newest OS versions, then you start losing compatibility and security, and are likely to go out and buy another one from them and they’ll make more money again. It is in their best interest to only provide OS updates for a couple of years. This planned obsolescence is their version of a subscription or residual income so their market doesn’t dry up.
As evidence that it is the manufacturers who are to blame, some people have even been able to “sideload” newer OS’s onto their old phones even though the manufacturer doesn’t “allow” it. When my Samsung Galaxy Note 8 refused to allow me to update past Android 9, I searched online for a walkthrough to figure out how to force it to allow me to use Android 10, and even Android 11. Samsung wouldn’t allow it because they want people to buy a new phone, but Android 10 and 11 work perfectly fine on this “OLD” device if they would allow it. Many people keep side-loading newer OS’s on their older phones. (Note, While this could possibly resolve some people’s issues, I can’t recommend anyone do this, particularly if you are not technically inclined, because of the intricacies involved…it’s complex and one needs to ensure the right drivers and such will be accounted for…let alone know how to manually install such updates, etc. I’m simply pointing out that it’s really not the AGE of the device that is the problem, it’s that phone manufacturers are trying to force people to buy new phones from them, it’s their version of a subscription model…planned obsolescence even if the device is still quite capable).
Some of them will provide certain “security updates” longer, but these are patching up certain flaws in the protocol and older code (solely to avoid minimum liability issues), and aren’t ACTUALLY giving you the NEW more improved security and related features found in the later OS versions that they won’t allow you to update to. That’s part of the difference. It’s not quite the same and not really as secure as newer ones.
That’s the problem here. Android 6 and below are severely lacking in many newer critical security and other improved critical features and support for certain protocols, and thus they become incompatible and less secure even when one has received an alleged “security update” we can only get updated security for the limited older OS and features and not the improved security that comes only with the latest OS’s which are not even on or supported by the older OS on those older devices.
It is very sad because in theory devices from 6+ years ago or some from even a decade ago COULD use the latest OS’s and run Wyze’s App, etc…In this case, the main problem is less about app developers (like Wyze) or the age of the device directly, and more about how device manufacturers would basically lose money and eventually go broke if they supported their devices forever. The device itself might keep functioning [offline] for decades to come but at some point it is not secure to use as a connected device anymore without the newer updates and protocols.
Connected app developers (as opposed to offline apps or those that are really simple or don’t need much security because their data risks are small) are faced with a Catch-22…a choice of supporting those old devices and getting yelled at for increased security leaks & problems, or making people upgrade to the new secure protocols and features and getting yelled at for not supporting the older devices. Either way they’re going to get bad publicity and anger a bunch of people.
Anyway, that’s an over-simplification…but in the end BerMM is totally correct that the decision is not based on device age, it is based on capability and security support level, which, in this case means a minimum of Android 7 or iOS 12 so that they will support critical features and security. Since Android 7 was released summer 2016, and iOS in Fall of 2018, any devices created after that should be compatible with minimum security, protocol and feature standards. Anything earlier than that will completely depend on whether the individual manufacturer ALLOWED a person to update to the newer OS’s or if the phone brand stopped allowing further OS updates. Some allow updates longer than others. Some phones NEVER allow you to ever upgrade to a newer OS than the one it shipped with, and will only give security patches for a short time. While others like Google are now promising security patches for 5 years for the Pixel 6…the longest of any Android-based manufacturer, and 3 years of software updates. All others do less than Google. Hence, saying if you have an android phone that is X years old or longer is a safe guess that it wouldn’t be supported because no other manufacturers provide updates. So if it’s a manufacturer that doesn’t do software updates, then if you bought the phone before Summer 2016 (5.5yrs ago), then your phone probably has Android 6 and your phone manufacturer burned you. If your phone manufacturer provides 1-2 years of software updates (some do this), then You would need a device made prior to summer 2014-2015. If you have a phone older than 2014-2016, it may be a great, capable piece of hardware, but if your manufacturer isn’t allowing you to upgrade to newer software, it’s become insecure and risky to use as a connected device…not because it’s not capable, but because nobody is supporting it to be secure anymore and it is missing all the latest security and other features needed to keep up in the industry. That’s the problem. It should still work well for making calls, texting through SMS (which is also not secure) instead of RCS, and using some offline or less data-critical connected apps…it might meet the limited needs for MANY people…but it’s missing too much for a lot of the really important and secure stuff.
Best way to know, isn’t by age of device, it’s to go into settings and selecting the “ABOUT” information and see what OS the device has on it.
Hope that helps some people’s understanding of the catch-22 data-critical online app developers are stuck deciding. Wyze and other app companies would LOVE for phones from a decade ago to still work and get the latest OS to still be compatible. They don’t get any money out of us having to buy a newer phone…but the phone manufacturers want money and they have no incentive to keep supporting old phones that they are no longer making any money from, so they’re trying to force us to buy a new one. And since they ALL do the same thing, we can’t really punish one by buying from another because the new one we buy from will do the exact same thing to us too. They have no incentive to continue supporting old devices when nobody else does and they don’t get an ongoing income stream from it, so we’re stuck in this planned obsolescence cycle that forces everyone to buy new devices because the hardware manufacturers also want an ongoing income stream. If we somehow FORCED them to provide support and updates for longer, then they would raise costs to compensate for having to pay employees to continue doing work on those devices, so we might not have to buy new phones as often, but we’d force the initial cost of devices to sky-rocket, so either way we’d have to pay for it. Wyze gets nothing out of any of that, in a way they (and customers) are also collateral damage regardless of which choice they make.